STORY HIGHLIGHTS

Australia has been a staunch ally of the United States in Iraq and in the fight against the Islamic State group

US and Australian troops plan to step up training so they are "fully prepared" to answer challenges in the Pacific, US Vice President Joe Biden said today amid rising tensions over Beijing's claims in the South China Sea.

Speaking in Sydney after meeting Prime Minister Malcolm Turnbull, Biden said the two nations were a "genuine brotherhood" committed to "making sure the sea lanes are open and the skies are free for navigation".

"They are the life bloodlines of commerce and the economic growth worldwide," Biden said in the wake of last weeks ruling by a UN-backed tribunal against Beijings claims in the disputed waters.

Beijing asserts sovereignty over almost all of the South China Sea, despite rival claims from its Southeast Asian neighbours -- most notably US ally the Philippines, which took the case to the Hague-based Permanent Court of Arbitration.

The United States, like Australia, has no claims of its own in the South China Sea, but insists that all shipping has a right to pass through seas it regards as international waters.

"We also discussed the steps that Australia and the United States are taking so our troops can train more together and increase our interoperability so that we are fully prepared to respond to any challenges, any challenges, in the Pacific with a united front," Biden said.

"It is important we stand together," he added, as he stressed that the United States was a Pacific power and intended to remain so.

Turnbull used a short media briefing alongside Biden to announce that Australia was expanding its role in Iraq to include the training of law enforcement officers and police as well as its current training of the Iraqi army.

Australia has been a staunch ally of the United States in Iraq and in the fight against the Islamic State group.

Biden's visit, which comes as President Barack Obama enters the final months of his administration, ends on Wednesday when he travels to New Zealand.